Process for the preparation of storage stable aqueous formulations of anionic dyes: amon exchange resin treatment

Abstract

The invention relates to a process for the preparation of a storage stable aqueous formulation of anionic dyes, which process comprises treating the aqueous dye solution and/or dispersion with a polymeric anion exchanger, simultaneously and/or subsequently subjecting the resin-bonded dye to a mechanical wet grinding, in the presence of a nonionic dispersant, and adding to the resultant aqueous dispersion the assistants customarily present in the liquid dye formulations. The process makes it possible to precipitate anionic dyes in virtually quantitative yield from aqueous solution and to prepare storage-stable dye dispersions.

What is claimed is: 
     
       1. A process for the preparation of a storage stable aqueous formulation of anionic dyes, which process comprises treating the aqueous dye solution or dispersion with a polymeric anion exchange resin, simultaneously or subsequently subjecting the resin-bonded dye to a mechanical wet grinding, in the presence of a nonionic dispersant, and adding to the resultant aqueous dispersion the assistants customarily present in the liquid dye formulations. 
     
     
       2. A process according to claim 1, wherein the treatment of the dye with the anion exchanger and the wet grinding are carried out simultaneously. 
     
     
       3. A process according to claim 1, wherein said resin is a polymeric water-insoluble anion exchanger with a polystyrene matrix which is substituted by quaternary ammonium groups and is crosslinked by divinylbenzene or diethylene glycol dimethacrylate. 
     
     
       4. A process according to claim 1, wherein the wet grinding is carried out in the presence of an ethylene oxide/propylene oxide block polymer with a molecular weight of 6000 to 22,500 and having the structural formula ##STR11## as nonionic dispersant, in which formula the indices a, b and c denote a whole number, with the proviso that the sum of a+c is a number from 100 to 400 and b is a number from 30 to 80. 
     
     
       5. A process according to claim 1, wherein the nonionic dispersant is used in an amount of 10 to 80% by weight, based on crude dye. 
     
     
       6. A process according to claim 1, wherein the resin-bonded dye is freed from water-soluble salts and by-products before or after the wet grinding. 
     
     
       7. A process according to claim 1, wherein the anion exchange resin has a particle size of <10 μm and the resin-bonded dye is mixed, without wet grinding, with a nonionic dispersant and the assistants customarily present in disperse liquid formulations and, in an optional further step, the dye/ion exchange resin dispersion is freed from water-soluble inert salts and by-products, before or after the addition of said assistants. 
     
     
       8. A process according to claim 6, wherein the removal of water-soluble salts and by-products is carried out by means of a membrane separation process. 
     
     
       9. A process according to claim 7, wherein the removal of water-soluble salts and by-products is carried out by means of a membrane separation process. 
     
     
       10. A process according to claim 1, wherein the assistants customarily added to liquid dye formulations are those selected from the group consisting of antifreeze agents, humectants, dispersants, viscosity improvers or microbicides. 
     
     
       11. A storage-stable dye dispersion obtained by a process as claimed in claim 1. 
     
     
       12. A process for dyeing or printing natural or synthetic fiber material which comprises contacting said material with an aqueous dye formulation prepared by the process of claim 1. 
     
     
       13. A process according to claim 8 wherein said membrane separation process is hyperfiltration. 
     
     
       14. A process according to claim 9 wherein said membrane separation process is hyperfiltration.